Pressure transmitters and other pressure sensing instruments include a pressure sensor that senses pressure in a process fluid. The pressure sensor provides an electrical output on leads to an electrical circuit that generates a pressure transmitter (or pressure instrument) output in a standardized electrical format.
There is a desire to have the electrical output of the pressure sensor be substantially free of errors due to environmental conditions surrounding the pressure sensor. In practice, however, isolation of the pressure sensor from its environment is difficult and results in large and expensive mounting structures for pressure sensors.
Errors can be introduced by stress on the sensor from its mounting, from electrical leads, and from the high temperatures of process fluids that present temperature gradients. Errors can also be introduced by corrosion or contamination of the sensor and its leads by chemicals in the process fluids. Errors can also be introduced due to stray electrical currents flowing from electrical leads to the environment. The sensor includes multiple isolation structures for connection to the pressure, connection to electrical leads, and for mounting to provide mechanical support for the sensor.
A low cost way of mounting and isolating a pressure sensor is needed that is compatible with high temperature, corrosive or contaminating process fluids and electrical isolation requirements and which reduces the cost and complexity of multiple isolation structures.